1. Field of the Invention
The present invention relates to an image sending apparatus and an image receiving apparatus for sending and receiving code sequence data.
2. Description of the Related Art
Conventionally, there exists a moving image delivering technology in which a client sends a transfer request of moving image data to a server, a server provides the moving image data, and the client reproduces the moving images by using the received moving image data. In the technology, for receiving moving image data from the server and reproducing moving images by the client, “download reproducing” and “stream reproducing” are known.
The download reproducing is to reproduce data downloaded into a buffer in the client from the server. According to this type, since the data which are once stored in the buffer are reproduced, there is a drawback in that the time length for reproducing moving image is short due to limitation of the memory capacity of the buffer. However, if the reproduction is performed after all data are received, there is an advantage in that the moving images can be reproduced regardless of process load of the server, the speed or traffic status of the transmission network, or the like.
On the other hand, according to the stream reproducing, a reproducing apparatus in the client side continuously requests data from the server, and the reproducing apparatus reproduces moving images in parallel with buffering the received data. According to this type, since the client continuously receives moving image data, the client reproduces the data in the buffer and discards the data in parallel with overwriting new data to the buffer. Therefore, there is an advantage in that long time reproduction of moving images is available without being affected by the limitation of memory capacity of the buffer.
However, there is a drawback in that the load of the server may increase according to increase of the number of clients simultaneously accessing the server, and the quality of the moving images is susceptible to the speed of the transmission line. Thus, there is a possibility of causing serious problems in that the reproduction of moving images stops due to an increase in the load of the server or a decrease of the speed of the transmission line. Generally, to avoid the serious problems, a method of scalability is used in which capacity of moving image data is changed.
MPEG1/MPEG2/MPEG4 are specific for moving images, and Motion JPEG in which still images are treated as continuous frames are conventionally used as image compression and decompression algorithms. As for the latter coding method of motion still images, a new method called Motion JPEG2000 is being standardized recently as an international standard.
However, according to the conventional moving image delivering technologies, generally, contents to be delivered are stored for a plurality of scalabilities beforehand in the server, and the user selects the most appropriate scalability according to the transmission capability of the transmission line and to the reproducing capability of the client to perform streaming reproduction.
In this case, since the user who operates the client selects an appropriate scalability in consideration of limitations of the transmission line, the most appropriate scalability cannot be selected by determining the load of the server that delivers image data to a plurality of clients simultaneously. Thus, when the load of the server becomes too large, transmission of code sequence data to each client is likely to delay, so that there occurs a problem in that the moving image data to be reproduced does not remain in the buffer in the client and the reproduction of moving images is interrupted.
In addition, not only it is inconvenient for the user to select the appropriate condition in consideration of the limitation of the transmission line, but also there is a problem in that the condition cannot be changed while the data are reproduced when the condition is once selected. That is, if the transmission line is suddenly congested while the streaming reproduction is performed, arrival of image data is likely to delay against the speed of image reproduction in the client, so that there occurs a problem in that the moving image data to be reproduced does not remain in the buffer in the client and the reproduction of moving images is interrupted.